Structure for measurement of capacitance of ultra-thin dielectrics
a technology of capacitance measurement and ultra-thin dielectrics, which is applied in the direction of resistance/reactance/impedence, individual semiconductor device testing, instruments, etc., can solve the problems of inability to perform high-frequency measurements, difficult characterization of gate oxide thickness, and large scaled gate dielectrics that are experiencing exponential increase in the incidence of undesirable tunneling currents. , to achieve the effect of avoiding weaknesses
Inactive Publication Date: 2005-12-27
INT BUSINESS MASCH CORP
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Benefits of technology
Enables reliable in-line manufacturing measurements of capacitance, reducing test costs and time, and allowing for improved control of ultra-thin oxide processes, effectively characterizing thinner dielectrics with high leakage values.
Problems solved by technology
Gate dielectrics that have been scaled to very small values are experiencing an exponential increase in the incidence of undesirable tunneling currents, in which the gate dielectric fails to insulate the gate from the underlying substrate.
Ordinary test structures and test equipment are unable to perform such high-frequency measurements, making the characterization of gate oxide thickness a very difficult test, which is unable to be repeated in a manufacturing environment.
Method used
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Embodiment Construction
[0017]As mentioned above, the increased use of larger dielectric DC currents requires the use of higher frequency test devices when measuring capacitance in order for the displacement current to significantly exceed the DC leakage current. The invention uses an on-chip ring oscillator to provide a high-frequency signal together with a circuit which will allow measurement of the capacitance at very high frequencies using ordinary test probes and equipment. This circuit allows full C-V characterization, avoiding the weaknesses associated with the use of simple ring-oscillators as a means of capacitance extractions.
[0018]FIG. 1 is a schematic diagram of one example of the invention embodied in the circuit used for on-chip high-frequency capacitance characterization. While the following embodiment is designed to find the capacitance of a device (such as an ultra-thin gate oxide), the invention can also be used to measure gate length, channel width, flat-band voltage, interconnect capaci...
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Disclosed is an on-chip test device for testing the thickness of gate oxides in transistors. A ring oscillator provides a ring oscillator output and an inverter receives the ring oscillator output as an input. The inverter is coupled to a gate oxide and the inverter receives different voltages as power supplies. The difference between the voltages provides a measurement of capacitance of the gate oxide. The difference between the voltages is less than or equal to approximately one-third of the difference between a second set of voltages provided to the ring oscillator. The capacitance of the gate oxide comprises the inverse of the frequency of the ring oscillator output multiplied by the difference between the voltages, less a capacitance constant for the test device. This capacitance constant is for the test device alone, and does not include any part of the capacitance of the gate oxide. The measurement of capacitance of the gate oxide is used to determine the thickness of the gate oxide.
Description
BACKGROUND OF INVENTION[0001]1. Field of the Invention[0002]The present invention generally relates to an on-chip test circuit for testing the gate oxide capacitance and more particularly to a circuit that includes a ring oscillator to allow high frequency testing.[0003]2. Description of the Related Art[0004]As integrated circuit transistors are reduced in size (e.g., scaled), gate dielectrics continue to get thinner. Gate dielectrics that have been scaled to very small values are experiencing an exponential increase in the incidence of undesirable tunneling currents, in which the gate dielectric fails to insulate the gate from the underlying substrate. In addition, the increased use of larger dielectric DC currents requires the use of higher frequency test devices when measuring capacitance in order for the displacement current to significantly exceed the DC leakage current.[0005]For example, in 90 nm technology, the DC leakage has reached current densities on the order of 400 A / cm...
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IPC IPC(8): G01R27/26G01R31/26G01R31/28
CPCG01R31/2831G01R27/2605G01R31/2648G01R31/2851
InventorMACIEJEWSKI, EDWARD P.NGUYEN, PHUNG T.NOWAK, EDWARD J.
OwnerINT BUSINESS MASCH CORP